Casandra....You can purchase different borders at Lowe's or Home Depot. They can be metal that use spikes to nail in ground or they have a heavy plastic that looks like rock. We have the metal and my husband curves it so it's not just straight. Of course, you can use landscape timbers too.
I would put a strip of weed cloth in the bottom of the small trench that I dug to recess the stones.
Then hand set the stones and if they’re highly irregular, I would buy a stone chisel & even them out.
Dig a shallow trench (a few inches), then arrange the rocks in a pleasing border. Fill in holes with soil. I have both stone and brick borders.
I just finished putting a border of brick edging down my driveway and around various areas. I used a small tool called a flexrake hand tiller. It was the perfect width for this border. As I placed each section, I pushed soil against the front and back of the piece to stabilize it. You can do this with rocks, stone, or brick.
Prior to that I had the black edging. To put it in place, you drive it in with a hammer. It's probably the least expensive, quickest, and easiest option.
There are plastic borders that look like stone that you can also use.
My husband put garden blocks around our garden. First he dug down and leveled the ground. Then he put down the first row, "gluing" them together on the sides with PL Premium. Then he started the second row, staggering them and gluing them to the bottom ones and the ones on each side. Then he put in a third row doing the same thing. This small wall has held up to floor waters that have reach to about an inch from the top. We haven't lost any flowers, soil or mulch.